( )You never take the schoolwork seriously.It is about time that you __ harder.(1)studies(2)studied(3)studying(4)to study.?

(2) you should be studied=studied=(should be )omitte
(4)are to study harder=with great effort,work hard severely closely go hard with Prime Minister Xi hard upon harder, NOT hardest !!!

(2)

正確答案是(2) studied
這是「假設語氣」所以用「過去式」動詞。表示：現在應該做，但尚未做。

以下例句請參見柯旗化《新英文法》p.401
It's time children "went" to bed.
= It's time for children to go to bed now.
是孩子們該就寝的時候了。

It's time you "got" up.=是你該起床的時候了。

所以：
It is about time that you studied harder.=是你該用功的時候了。